A conventional bicycle hub generally includes a driving tube connected to one end thereof and an axle extends through the hub and the driving tube. The driving tube includes a ratchet portion and a sprocket portion, and at least one bearing is located between the axle and the hub to let the hub together with the driving tube rotate in one direction to drive the bicycle.
A bicycle hub assembly known to applicant generally includes a hub with a first end and a second end, and an axle extends through the hub. A passive unit is rotatably installed to a chamber in the first end of the hub and rotatable relative to the axle. A passive tube is fixed to the hub and mounted to the axle, multiple pawls are located in the chamber and connected to outside of the passive tube. A spring pushes the pawls. A driving unit is connected to the passive unit and rotatable relative to the passive unit. A driving tube is mounted to the passive tube and includes a ratchet section which is located in the chamber of the hub. A driving section extends from the ratchet section which includes multiple ratchet teeth which push the spring in one direction. The driving section has multiple rectangular teeth.
Another bicycle hub assembly known to applicant generally includes a passive unit which includes a passive frame that is rotatable about an axis. The passive frame includes restriction slots and resistance slots. A clutch unit includes pawls in the restriction slots and each pawl includes a pivotal portion which is pivotably connected to the restriction slot. Each pivotable portion has an engaging portion. The clutch unit further includes a spring which pushes the engaging portion outer from the restriction slot, and multiple resistance members located in the resistance slots. A driving unit includes a ratchet gear which is rotatably connected to the passive frame and the ratchet gear includes driving surface for driving the engaging portion to move the passive frame, and a pressing surface for pushing the engaging portion toward the restriction slots, and tips connected between the driving surface and the pressing surface. The tips contact the resistance members.
The first prior art includes ratchet teeth and the pawls so as to increase the torque of the rectangular teeth so that the first end of the hub does not need any thread to reduce the manufacturing cost. The second prior art provides pawls to drive the ratchet teeth in one direction and each ratchet tooth includes a tip which contacts the resistance member. When the pedal system of the bicycle fails to work, the initial force from the rear wheel makes the resistance member to jump off from the tip so as to let the passive unit to drive the driving unit such that the safety is enhanced.
The bearings that are cooperated with the two prior arts are installed off from the center of rotation of the ratchet unit, so that the ratchet unit tends to bias to one part than another. This increases friction and wastes energy. Besides, when using the bearing that includes beads retained by braces, too many parts are involved and is difficult to maintain.
The present invention intends to provide a bicycle hub assembly wherein the rotary members such as bearings are installed on the center of rotation of the ratchet unit and the sprocket unit so as to reduce the friction and increase smooth of rotation of the hub.